title: Novel insights into pancreatic β-cell glucolipotoxicity from real-time functional analysis of mitochondrial energy metabolism in INS-1E insulinoma cells.
abstract: High circulating glucose and non-esterified (free) fatty acid levels can cause pancreatic β-cell failure. The molecular mechanisms of this β-cell glucolipotoxicity are yet to be established conclusively. In the present paper we report on the involvement of mitochondrial dysfunction in fatty-acid-induced β-cell failure. We have used state-of-the-art extracellular flux technology to functionally probe mitochondrial energy metabolism in intact INS-1E insulinoma cells in real-time. We show that 24-h palmitate exposure at high glucose attenuates the glucose-sensitivity of mitochondrial respiration and lowers coupling efficiency of glucose-stimulated oxidative phosphorylation. These mitochondrial defects coincide with an increased level of ROS (reactive oxygen species), impaired GSIS (glucose-stimulated insulin secretion) and decreased cell viability. Palmitate lowers absolute glucose-stimulated respiration coupled to ATP synthesis, but does not affect mitochondrial proton leak. Palmitate is not toxic when administered at low glucose unless fatty acid β-oxidation is inhibited. Palmitoleate, on the other hand, does not affect mitochondrial respiration, ROS levels, GSIS or cell viability. Although palmitoleate protects against the palmitate-induced ROS increase and cell viability loss, it does not protect against respiratory and insulin secretory defects. We conclude that mitochondrial dysfunction contributes to fatty-acid-induced GSIS impairment, and that glucolipotoxic cell viability and GSIS phenotypes are mechanistically distinct.
authors.affiliation: *School of Biomedical and Healthcare Sciences, Plymouth University, Drake Circus, Plymouth PL4 8AA, U.K.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Barlow
authors.forename: Charles
authors.initials: C
authors.lastname: Affourtit
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000633:toxicity*; D005947:Glucose / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism* / Q000473:pathology; D007340:Insulinoma; D008928:Mitochondria / Q000378:metabolism* / Q000473:pathology; D010084:Oxidation-Reduction / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D019308:Palmitic Acid / Q000633:toxicity*; D018892:Proton-Motive Force / Q000187:drug effects*; D051381:Rats
chemical_list: D004791:Enzyme Inhibitors; D007328:Insulin; D019308:Palmitic Acid; D000255:Adenosine Triphosphate; D005947:Glucose